Pressure to clean up contaminated sites has continued under government regulation which requires removal, reduction, destruction, or stabilization of environmentally hazardous chemical compounds. However, certain groundwater contaminants are difficult to treat in a cost-effective manner. These contaminants gain a reputation as being “recalcitrant” primarily as a result of fundamental physicochemical properties that make treatment difficult.
Biodegradation (one potential method for remediating such contamination) involves using indigenous or introduced (i.e., non-indigenous) bacteria or other microbes to degrade or digest organic chemicals transported across their cell membranes, thereby producing byproducts such as carbon dioxide gas and water. Although biodegradation works well for certain organic contaminants, it can be difficult or impossible to biodegrade recalcitrant organic contaminants.
1,4-dioxane is one example of a recalcitrant organic contaminant. 1,4-Dioxane, otherwise referred to as simply “dioxane,” is a clear liquid that easily dissolves in water. It is used primarily as a solvent in the manufacture of chemicals and as a laboratory reagent and has various other uses that take advantage of its solvent properties. 1,4-Dioxane is a trace contaminant of some chemicals used in cosmetics, detergents, and shampoos. However, manufacturers now reduce 1,4-dioxane from these chemicals to low levels before these chemicals are made into products used in the home.
The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the nation. These sites are then placed on the National Priorities List (NPL) and are targeted for long-term federal clean-up activities. 1,4-Dioxane has been found in at least 31 of the 1,689 current or former NPL sites. Although the total number of NPL sites evaluated for this substance is not known, the possibility exists that the number of sites at which 1,4-dioxane is found may increase in the future as more sites are evaluated. Since 1,4-dioxane is considered a hazardous material that contaminates ground water, there is a need for a process that will remove 1,4-dioxane from groundwater. Previously, attempts have been made to use a combination of hydrogen peroxide and ultraviolet light (UV), or ozone in combination with UV light to destroy 1,4-dioxane. These processes are not very efficient and may require an additional post treatment step with peroxide to completely remove 1,4-dioxane. Another process used is a regenerable charred resin material that will adsorb 1,4-dioxane. However, this process results in a waste stream that contains concentrated 1,4-dioxane that requires another means to destroy the 1,4-dioxane such as incineration.